This invention relates to an apparatus designed to control the application of vacuum by vacuum sources to vacuum-operated devices and, in particular, to an apparatus designed to automatically protect such vacuum sources from contamination by aspiration of fluids or aerosols.
The use of vacuum pumps and similar vacuum sources in industrial, research and medical applications is widespread. For example, the aspiration of tissue culture media from cultures and of supernatants from centrifuge samples into collection vessels or reservoirs is a common procedure in many laboratories. The need for preventing accidental contamination of house vacuum systems or laboratory pumps by aerosols or fluids has long been recognized. Examples of prior attempts to protect such vacuum sources are desribed in "Environmental Control Notes," No. 3, February 1972 , published by the Environmental Services Branch, Division of Research Services, National Institutes of Health. This publication describes previous systems and suggests the use of a disposable, cartridge-type filter to entrap submicron virus aerosols and protect the vacuum source from contamination. In connection with the filter, the use of a float-type vacuum break to prevent contamination by aspirated fluids is also suggested.
There are, however, significant disadvantages in using the above system. A float-type or gravity operated vacuum shutoff operation is not entirely reliable since it depends upon the ability of a rubber bulb to rise with the aspirated fluid and consistently seat itself so as to fluid-tightly stopper a Buchner funnel. The vacuum break does not occur until the fluid rises almost to the mouth of the funnel. In addition, there is no means of forcing the aspirated fluid back into the primary reservoir from the secondary reservoir, nor is the application of vacuum completely broken, only temporarily blocked.